Heat grill to medium high. Sear skirt steak on both sides and cook to desired temperature, set aside. Heat a large skillet over medium heat, add the butter and once melted, add onions and garlic. Let the onions sauté for a few minutes, then add the mushrooms. Cook until the mushrooms are golden, then add the flour and stir. Add the beef broth, Dijon, and sour cream. Allow to simmer, then reduce the heat and continue to cook for several minutes, until the sauce thickens. Adjust seasonings and add the beef into the sauce to warm through. Serve over egg noodles and garnish with parsley, thyme, and crispy garlic.